TWI626422B - Measuring method, radiation source, metering device and device manufacturing method - Google Patents

Abstract

The structure is detected by at least the first application of EUV radiation (304) generated by inverse Compton scattering by lithography or by using one of the target structures (T) in lithography. Detect (312) the radiation (308) scattered by the target structure in reflection or transmission, and calculate a property of the target structure based on the detected scattered radiation by a processor (340). The radiation may have a first wavelength in an EUV range of 0.1 nm to 125 nm. In the case of using the same source and controlling the energy of an electron, it can be irradiated with different wavelengths in the EUV range and / or with shorter (x-ray) wavelengths and / or with longer (UV light, visible light) wavelengths This structure multiple times. By quickly switching the electron energy in an inverse Compton scattering source, irradiation at different wavelengths can be performed several times per second.

Description

Measuring method, radiation source, measuring device and device manufacturing method

The present invention relates to a metering method and device that can be used for, for example, device manufacturing by lithographic technology, and to a method of manufacturing a device using lithographic technology. The method of measuring the critical dimension (line width) is described as a specific application for this measurement. For the purposes of the present invention, metrology includes detection for a wide range of purposes, including, for example, the detection of defects, rather than just quantitative measurements of specific dimensions or material properties.

A lithographic apparatus is a machine that applies a desired pattern onto a substrate (typically onto a target portion of the substrate). Lithography devices can be used, for example, in integrated circuit (IC) manufacturing. In that case, a patterned device (which is alternatively referred to as a reticle or a reticle) can be used to generate a circuit pattern to be formed on individual layers of the IC. This pattern can be transferred to a target portion (eg, a portion including a die, a die, or a number of die) on a substrate (eg, a silicon wafer).

In the lithography process, the measurement of the generated structure is frequently required, for example, for program control and verification. Various tools for making such measurements are known to us, including a scanning electron microscope (SEM) that is often used to measure critical dimensions (CD). Other specialization tools are used to measure parameters related to asymmetry. One of these parameters is a stacked pair (alignment accuracy of two layers in the device). Recently, various forms of scatterometers have been developed for use in the field of lithography. These devices direct the radiation beam onto the target and measure one or more properties of the scattered radiation-for example, the intensity at a single reflection angle that varies depending on the wavelength; Intensity at one or more wavelengths that varies depending on the angle of reflection; or polarization that varies depending on the angle of reflection--to obtain a "spectrum" of the attribute of interest that can be used to determine the target. The determination of the attribute of interest can be performed by various techniques: for example, reconstruction of the target structure by iterative approaches such as tightly coupled wave analysis or finite element methods; library search; and principal component analysis. Compared to SEM technology, optical scatterometers can be used at a much higher yield on a large proportion or even all product units.

However, as technology develops, performance specifications become more stringent. One of the current methods is additionally limited to the use of optical wavelengths to perform these methods, which requires a dedicated metrology structure that is much larger than the typical size of actual product features. Therefore, measurements made on these metering structures only indirectly indicate the actual product structure. A particular parameter of interest is line width (CD), and a suitable small target method for CD measurement has not been designed.

In order to obtain higher resolution measurements, the use of EUV radiation having a wavelength in the range of, for example, 0.1 nm to 125 nm has also been considered. EUV radiation is particularly attractive because it has a wavelength of the same order of magnitude as the structure to be measured. For example, a spectral EUV reflection measurement is proposed in European Patent Application No. 15160786, which was not published at the priority date. Unfortunately, due to the limitation of available radiation sources, there is no such thing as a measurement of small targets (such as intra-grain gratings or the product structure itself) at a rate suitable for mass measurement in high-volume manufacturing. Existing technology. The ideal radiation source will be dense and affordable, with high brightness coupled to a freely selected wavelength and good ability to focus into a small target area.

Bright compact x-ray sources have recently been described based on the inverse Compton scattering (ICS) phenomenon. This x-ray source was described by WS Graves et al. In "Compact x-ray source based on burst-mode inverse Compton scattering at 100 kHz" (Physical Review Special Topics-Accelerators and Beams 17, 120701 (2014)). The entire reference and related patent application by Graves et al. Is incorporated herein by reference. In order to achieve high electronic brightness, a linear accelerator is used to achieve High brightness ideal for high-volume applications. Details of linear accelerators used in x-ray sources are provided in published patent application US2014191654A1 (Tantawi and Nelson). Other ways to accelerate electronics are being developed by other workers.

The present invention aims to provide an alternative method of small target metrology to overcome one or more of the disadvantages of the optical and X-ray methods described above. It is specifically required to measure, for example, parameters at locations within a product area on a semiconductor substrate, while improving the speed at which such measurements can be performed, and at the same time adapting to the smaller features of current and future lithographic technology size.

The present inventors have recognized that sources based on inverse Compton scattering can be adapted to provide bright and controllable sources in the EUV (soft X-ray) range to achieve large-volume metering of small targets. This adapted source can be used to detect other types of structures (both natural and man-made), not just semiconductor products.

The invention provides, in a first aspect, a method for measuring an attribute of a structure, the method comprising: irradiating the structure with radiation at least for the first time; detecting the radiation after interacting with the structure; An attribute of the structure is determined based on an attribute of the radiation, wherein the radiation is generated by inverse Compton scattering, and the radiation has a first wavelength in a range of 0.1 nm to 125 nm.

The invention further provides a radiation source device based on inverse Compton scattering, the device comprising: an electron source and a photon source; and a controller for controlling the electron source and the photon source to convert one or more The electron beams are simultaneously delivered to a point of interaction with a pulse of the photon, whereby a proportion of the photons obtain extra energy by inverse Compton scattering to the device and the device outputs the photon of the photon. A ratio in which the additional energy can be controlled such that the photons output by the device have a wavelength in the range of 0.1 nm to 125 nm.

The inventors have recognized that a source based on inverse Compton scattering can be designed and controlled It delivers radiation over a very wide range of wavelengths, not just EUV wavelengths and / or x-rays. The source is, for example, operable to provide radiation in EUV, UV, and even visible light wavelengths and / or x-ray wavelengths in addition to radiation at EUV wavelengths.

The invention further provides a measuring device for measuring the properties of a structure, the device comprising: a radiation source device according to the invention as explained above; and a lighting system for photons output by the radiation source device Delivered to the structure in a radiation beam; and a detection system for detecting radiation from the structure after the photons have interacted with the structure.

In a particular implementation, the device is adapted to receive semiconductor wafers (eg, 300 mm wafers) from an automated wafer handler. In other applications, the device can be adapted to measure any type of structure, whether natural or artificial.

In yet another aspect, the present invention provides a device manufacturing method, comprising: using a lithography process to transfer a pattern from a patterned device to a substrate, the pattern defining at least one periodic structure; measuring the Periodic structure of one or more attributes to determine a value of one or more parameters for the lithography process; and applying a correction in subsequent operations of the lithography process based on the measured attributes, wherein the measurement is The step of the attributes of the periodic structure includes measuring an attribute by a method according to the invention as explained above.

Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings. It should be noted that the invention is not limited to the specific embodiments described herein. These embodiments are presented herein for illustrative purposes only. Based on the teachings contained herein, additional embodiments will be apparent to those skilled in the relevant art.

200 ‧ ‧ lithography device LA / lithography tools

202‧‧‧Measuring station MEA

204‧‧‧Exposure Station EXP

206‧‧‧LACU

208‧‧‧coating device

210‧‧‧Baking device

212‧‧‧Developing device

220‧‧‧ patterned substrate

222‧‧‧Processing equipment / etching equipment

224‧‧‧treatment equipment / annealing equipment

226‧‧‧Processing device / step

230‧‧‧ substrate

232‧‧‧ substrate

234‧‧‧ substrate

238‧‧‧Supervisory Control System (SCS)

240‧‧‧metering device / optical scatterometer

242‧‧‧Measurement results

244‧‧‧EUV measuring device

246‧‧‧Measurement results

300‧‧‧ extreme ultraviolet (EUV) metering device

302‧‧‧circle

304‧‧‧ Incident radiation / EUV radiation

306‧‧‧circle

308‧‧‧Reflected rays / radiation

310‧‧‧Scattered rays / spectrum

312‧‧‧light detector

330‧‧‧ radiation source

332‧‧‧lighting system

333‧‧‧ Detection System

334‧‧‧Positioning System

336‧‧‧movable support

338‧‧‧Second Detector

340‧‧‧Processor

400‧‧‧ high energy electron beam

401‧‧‧laser radiation / laser beam

402‧‧‧Radio frequency (RF) electron gun

404‧‧‧linac

406‧‧‧Focus Assembly

408‧‧‧Beam Deflector

410‧‧‧Electronic stopper

412‧‧‧optical pulse

414‧‧‧photocathode laser

416‧‧‧Seed Laser

420‧‧‧Inverse Compton Scattering (ICS) Laser

422‧‧‧output beam

424‧‧‧Optical cavity

426‧‧‧mirror mirror

428‧‧‧Mirror

430‧‧‧ lens

432‧‧‧Harmonic generator

440‧‧‧output beam / radiation beam

442‧‧‧Focusing Optics / Optics

450‧‧‧ Klystron

452‧‧‧waveguide system

454‧‧‧Control System

602‧‧‧ radiation beam / incident beam

604‧‧‧ Beam

620‧‧‧first pore

622‧‧‧ incident beam

624‧‧‧Two-dimensional curved mirror

626‧‧‧ Converging Beam

630‧‧‧Second pore

632‧‧‧beam

634‧‧‧Reflected beam

636‧‧‧Second focusing mirror / two-dimensional curved mirror

700‧‧‧ edge

702‧‧‧wavelength

704‧‧‧wavelength

710‧‧‧Edge

720‧‧‧Edge

722‧‧‧Edge

730‧‧‧Edge

732‧‧‧wavelength

734‧‧‧wavelength

900‧‧‧ target area

1300‧‧‧ Transmission mode (T-SAXS) measuring device

1304‧‧‧ radiation beam

1312‧‧‧ Detector

α‧‧‧ incident angle

B‧‧‧ oval

B'‧‧‧ ellipse / beam

CD‧‧‧ critical size

D‧‧‧ direction

d _b ‧‧‧beam diameter

d _s ‧‧‧beam diameter

IP‧‧‧Interaction point

MA‧‧‧ Patterned Device / Photomask

N‧‧‧ direction

R‧‧‧ Recipe Information

S‧‧‧ Focused radiation spot / round spot

S'‧‧‧ light spot

S21‧‧‧step

S22‧‧‧step

S23‧‧‧step

S24‧‧‧step

T‧‧‧Measurement target / target structure

W‧‧‧ substrate

Embodiments of the present invention will now be described with reference to the accompanying drawings as examples, in which: FIG. 1 depicts a lithographic apparatus along with other devices forming a production facility for a semiconductor device; FIG. 2 illustrates The geometry of the incident and reflected rays with respect to the grating target in the metrology method of the first embodiment; FIG. 3 schematically illustrates the components of a metrology device that performs the method of FIG. 2; FIG. The structure of the radiation source in the device; FIG. 5 shows the components of the radiation source of FIG. 4 in more detail; FIG. Schematic representations of beam cross sections B and light spots S for different angles of incidence are schematically shown at (b) and (c); FIG. 7 schematically illustrates the lighting system in one embodiment of the device of FIG. 3 Figure 8 illustrates changes in the absorptance for different materials throughout a wavelength range in the EUV spectrum; Figures 9 to 12 illustrate various application modes of the device of Figure 3; Figure 13 illustrates the use of an ICS source to perform transmission Small angle x-ray scattering The modified apparatus; and FIG. 14 is a diagram used for measuring by the method of FIG. 14 is a control flowchart to measurement methods and / or efficacy of methods of photolithography manufacturing process.

Before describing embodiments of the invention in detail, it is instructive to present an example environment in which embodiments of the invention can be implemented.

FIG. 1 shows the lithographic apparatus LA at 200 as a part of an industrial facility implementing a large-capacity lithographic manufacturing process. In this example, the manufacturing process is adapted for Semiconductor products (integrated circuits) are manufactured on round substrates. Those skilled in the art will understand that a wide variety of products can be manufactured by processing different types of substrates using variations of this process. The production of semiconductor products is purely used as an example of great commercial significance today.

In the lithography installation (or, in short, the "lithography tool" 200), the measurement station MEA is displayed at 202 and the exposure station EXP is displayed at 204. The control unit LACU is shown at 206. In this example, each substrate visits a measurement station and an exposure station to have an applied pattern. For example, in an optical lithography device, a projection system is used to transfer a product pattern from the patterning device MA to a substrate using an adjusted radiation and projection system. This transfer is accomplished by forming a patterned image in a layer of radiation-sensitive resist material.

As used herein, the term "projection system" should be interpreted broadly to cover any type of projection system, including refraction, reflection, suitable for the exposure radiation used or other factors such as the use of immersion liquids or the use of vacuum , Refraction, magnetic, electromagnetic, and electrostatic optical systems, or any combination thereof. The patterning device MA may be a photomask or a reduction mask that imparts a pattern to a radiation beam transmitted or reflected by the patterning device. Well-known operation modes include step mode and scan mode. As is well known, projection systems can cooperate with support and positioning systems for substrates and patterned devices in a variety of ways to apply a desired pattern across a substrate to many target portions. Programmable patterning devices can be used instead of masks with fixed patterns. Radiation, for example, may include electromagnetic radiation in deep ultraviolet (DUV) or extreme ultraviolet (EUV) bands. The present invention is also applicable to other types of lithographic processes, such as embossed lithography and write-through lithography (for example, by an electron beam).

The lithographic device control unit LACU controls all movements and measurements of various actuators and sensors for accommodating the substrate W and the mask MA and performing a patterning operation. LACU also includes the signal processing and data processing capabilities needed to implement the calculations required in connection with the operation of the device. In practice, the control unit LACU will be implemented as a system of many sub-units, and each sub-unit handles real-time data acquisition, processing, and control of a subsystem or component within the device.

Before applying the pattern to the substrate at the exposure station EXP, process the substrate at the measurement station MEA Plate so that various preliminary steps can be performed. The preliminary steps may include using a level sensor to map the surface height of the substrate, and using an alignment sensor to measure the position of the alignment mark on the substrate. The alignment marks are nominally arranged in a regular grid pattern. However, the marks deviate from the ideal grid due to inaccuracy in generating the marks and also due to deformation of the substrate that occurs through processing through the substrate. Therefore, in addition to measuring the position and orientation of the substrate, the alignment sensor must also measure the positions of many marks across the substrate area in detail (the device will print product features at the correct location with extremely high accuracy) in the case of). The device may be of the so-called dual stage type with two substrate stages, each substrate stage having a positioning system controlled by a control unit LACU. While exposing one substrate on one substrate stage at the exposure station EXP, another substrate can be loaded on the other substrate stage at the measurement station MEA, so that various preliminary steps can be performed. Therefore, the measurement of the alignment marks is extremely time consuming, and providing two substrate stages will achieve a considerable increase in the yield of the device. If the position sensor cannot measure the position of the substrate table when the substrate table is at the measurement station and the exposure station, a second position sensor may be provided to enable the position of the substrate table to be tracked at two stations . The lithographic apparatus LA may, for example, belong to the so-called dual stage type, which has two substrate stages WTa and WTb and two stations (exposure station and measurement station), between which the substrate stage can be exchanged .

In the production facility, the device 200 forms part of a "lithographic manufacturing unit" or "lithographic cluster", and the "lithographic manufacturing unit" or "lithographic cluster" also contains a coating device 208 for applying photosensitive resist Agents and other coatings are applied to the substrate W for patterning by the device 200. At the output side of the device 200, a baking device 210 and a developing device 212 are provided for developing the exposed pattern into a solid resist pattern. Among all these devices, the substrate handling system focuses on supporting the substrate and transferring the substrate from one piece of the device to the next. These devices, often collectively referred to as the coating and developing system (track), are under the control of the coating and developing system control unit, which is itself controlled by the supervisory control system (SCS) 238, and the supervisory control system SCS The lithographic device is also controlled via the lithographic device control unit LACU. Therefore, different devices can be operated to maximize output and Processing efficiency. The supervisory control system SCS receives the recipe information R, which provides in great detail the definition of the steps to be performed to produce each patterned substrate.

Once the pattern has been applied and developed in the lithographic unit, the patterned substrate 220 is transferred to other processing devices (such as illustrated at 222, 224, 226). A wide range of processing steps is performed by various devices in a typical manufacturing facility. For the sake of example, the device 222 in this embodiment is an etching station, and the device 224 performs a post-etching annealing step. Other physical and / or chemical processing steps are applied to other devices 226 and the like. Numerous types of operations may be required to fabricate actual devices, such as material deposition, modification of surface material properties (oxidation, doping, ion implantation, etc.), chemical mechanical polishing (CMP), and so on. In practice, the device 226 may represent a series of different processing steps performed in one or more devices.

It is well known that the manufacture of semiconductor devices involves many iterations of this process to build device structures with appropriate materials and patterns layer by layer on a substrate. Thus, the substrate 230 arriving at the lithographic cluster may be a newly prepared substrate, or it may be a substrate that has previously been completely processed in this cluster or in another device. Similarly, depending on the required processing, the substrate 232 leaving the device 226 may be returned for subsequent patterning operations in the same lithographic cluster, it may be designated for patterning operations in different clusters, or it may be The finished product to be sent for dicing and packaging.

Each layer of the product structure requires a different set of procedural steps, and the devices 226 used at each layer may be completely different in type. In addition, even in the case where the processing steps to be applied by the device 226 are nominally the same in a large facility, there may be several assumptions that the same machines work in parallel to perform the steps applied by the device 226 on different substrates. Small differences in settings or failures between these machines can mean that they affect different substrates in different ways. Even if the steps are relatively common to each layer, such as etching (device 222) may be performed by several etching devices that are nominally the same but working in parallel to maximize the yield. In addition, in practice, different layers require different etching procedures according to the details of the material to be etched, for example, chemical etching, plasma etching, and require specific requirements, such as anisotropic etching.

The previous and / or subsequent procedures may be performed in other lithographic devices (as mentioned just now), and the previous and / or subsequent procedures may even be performed in different types of lithographic devices. For example, some layers in the device manufacturing process that require extremely high parameters such as resolution and overlap can be performed in more advanced lithography tools than other less demanding layers. Therefore, some layers can be exposed in an immersion lithography tool, while others are exposed in a "dry" tool. Some layers can be exposed in tools working at DUV wavelengths, while others are exposed using EUV wavelength radiation.

In order to correctly and consistently expose a substrate exposed by a lithographic apparatus, it is necessary to detect the exposed substrate to measure properties such as an overlay error between subsequent layers, a line thickness, a critical dimension (CD), and the like. Therefore, the manufacturing facility where the lithographic manufacturing unit LC is located also includes a metrology system MET, which stores some or all of the substrates W that have been processed in the lithographic manufacturing unit. The measurement results are provided directly or indirectly to the supervisory control system SCS. If an error is detected, the exposure of subsequent substrates can be adjusted, especially if the measurement can be performed quickly and quickly enough that other substrates of the same batch are still to be exposed. In addition, the exposed substrate can be stripped and reworked to improve yield, or discarded, thereby avoiding further processing of known defective substrates. In a situation where only some target portions of the substrate are defective, further exposure may be performed only on good ones of the target portions.

Figure 1 also shows a metering device 240 that is provided for measuring parameters of a product at a desired stage during a manufacturing process. A common example of a metering device in a modern lithographic production facility is a scatterometer (e.g., an angular resolution scatterometer or a spectral scatterometer), and it can be applied to measure a developed substrate at 220 before etching in the device 222 Properties. Where a metering device 240 is used, it can be determined that, for example, important performance parameters such as overlay or critical dimension (CD) do not meet the specified accuracy requirements in the developed resist. Prior to the etching step, there is an opportunity to strip the developed resist via a lithographic cluster and reprocess the substrate 220. It is also well known that by supervising the control system SCS and / or the control unit LACU 206 with minor adjustments over time, metering from the device 240 can be used The result 242 is to maintain the accurate performance of the patterning operation in the lithography cluster, thereby minimizing the risk of making substandard products and requiring heavy work. Of course, the measuring device 240 and / or other measuring devices (not shown in the figure) may be applied to measure the properties of the processed substrates 232 and 234 and the incoming substrate 230.

Each generation of lithographic manufacturing technology (commonly referred to as a technology "node") has stricter specifications for performance parameters such as CDs. One of the main challenges in metrology is the requirement that the size of the metrology target be smaller than that typically used with the metrology device 240. For example, the current goal should be to use a target with a size of 5 microns x 5 microns or less. These small sizes will allow the more extensive use of so-called "in-grain" metrology where the target is located within the product characteristics (instead of being restricted to the area of the cut path between product areas); or "on-product" metrology where the target For the product structure itself. The only measurement technique currently used for CD measurement on products is the electron microscopy (CD-SEM). This known technique demonstrates restrictions on future nodes and only provides extremely limited geometric information of the structure.

One way to improve the measurement of the smallest structure would be to use shorter wavelength radiation such as in the extreme ultraviolet (EUV), soft x-ray, or even hard x-ray range. For example, an EUV reflection measurement including a spectral EUV reflection measurement can be considered as a CD measurement method for future technology nodes. X-ray scattering techniques such as small-angle x-ray scattering can also be considered in transmission mode (T-SAXS) or in grazing incidence mode (GI-SAXS). The principle and practice of EUV measurement in the context of this content are provided in the aforementioned patent application EP15160786. It demonstrates the benefits of EUV reflection measurements that provide high sensitivity, robustness against program changes, and selectivity for the parameter of interest.

For the purposes of the present invention, hard x-rays are considered to be rays having a wavelength of less than about 0.1 nanometer (for example, including the range of 0.01 nanometer to 0.1 nanometer). Soft x-ray or EUV refers to a range extending approximately from a wavelength of 0.1 nm to 125 nm. The different sub-ranges of these ranges may be selected to be of a size suitable for the structure under investigation. For example, for semiconductor structures subject to the limitations of current lithography technology, consider the range of 0.1 nm to 20 nm, or 0.1 nm Wavelengths in the range of meters to 10 nanometers or in the range of 1 nanometer to 5 nanometers. Not only the size of the structure, but also the material properties of the structure can influence the choice of wavelengths for use in investigations. For example, in order to perform a reflection measurement, at least the background material of the structure needs a good reflection intensity at the wavelength used. In order to investigate buried characteristics, the wavelength should be selected to obtain sufficient penetration through the overlying material.

EUV metering can be used to measure structures (post-development inspection or ADI) in resist materials processed in lithographic manufacturing units, and / or to measure structures after they have been formed from harder materials (etching Post-test or AEI). For example, the substrates may be inspected using the EUV metering device 244 after the substrates have been processed by the developing device 212, the etching device 222, the annealing device 224, and / or other devices 226. X-ray technology is usually limited to AEI due to poor contrast in resist materials at x-ray wavelengths.

For high-volume manufacturing applications, high-brightness radiation sources will be required to reduce the acquisition time for each measurement. The limited capabilities of current dense x-ray sources means that known T-SAXS technologies suffer from extremely low output rates, especially for small and large metrology targets. This is especially the case when we try to obtain a very small spot size for a small target area on a lighting substrate. EUV sources are also known to be limited in brightness and limited in wavelength selection. In order to maximize the contrast in the target structure and to distinguish the structures of different materials, fine control of wavelengths over a wide range will be required.

The manufacturing system illustrated in FIG. 1 includes one or more EUV metering devices 244 in addition to the optical scatterometer 240. This EUV measurement device provides additional measurement results 246, which can be used by the supervisory control system SCS to achieve further control of quality and improvement of the overall performance of the lithographic manufacturing system. Similar to the optical scatterometer 240, the metering device 244 may be applied at different manufacturing stages mentioned above, such as ADI and AEI.

EUV reflection measurement method

FIG. 2 illustrates a metering method, and FIG. 3 illustrates a metering device 300. This device can be used as a practical EUV metering device 244 for measuring the parameters of the substrate W processed in the manufacturing system of FIG. 1 example. The device can be used in bands other than EUV.

In FIG. 2, the target T is schematically represented as a one-dimensional grating structure at the origin including a spherical reference frame. The axes X, Y, and Z are defined relative to the target. (Of course, any arbitrary coordinate system can be defined in principle, and each component can have its own local reference frame that can be defined relative to the reference frame shown). Align the periodic direction D of the target structure with the X axis. The diagram is not a real perspective view, but is only a schematic illustration. The X-Y plane is the plane of the target and the substrate, and is shown to be tilted towards the viewer for clarity, which is represented by the tilted view of circle 302. The Z direction defines a direction N perpendicular to the substrate. In FIG. 2, the incident radiation is labeled 304 and has a grazing incidence angle α. In this example, the incident ray 304 (and all incident rays forming the radiation spot S) is substantially in a plane parallel to the X-Z plane, which is a plane defining directions D and N and represented by a circle 306. Reflected rays 308 (ie, specularly reflected rays) that are not scattered by the periodic structure of the target T appear toward the right side of the target in the figure, which has an elevation angle α.

According to the diffraction properties of the target, other rays 310 are scattered at an angle different from the specular reflection. The separation angle between these rays and specularly reflected rays will depend on the relationship between the wavelength of the radiation and the characteristic interval of the target. The drawing is not to scale. For example, the detector 312 may be closer or farther away from the target than the situation shown, and the target grating will likely be extremely small relative to the detector; the diffraction angle of the ray 310 may be much wider than the indicated angle.

To perform reflection measurements, rays 308 and / or scattered rays 310 are captured by a light detector 312. The detector 312 includes, for example, a position-sensitive EUV detector, which is typically an array of detector elements. The array can be a linear array, but a two-dimensional array of elements (pixels) can be provided in practice. For example, the detector 312 may be a charge coupled device (CCD) image sensor or a CMOS image sensor. This detector is used to transform the reflected radiation into an electrical signal and finally into digital data for analysis. A single pixel detector is sufficient in principle for some types of measurements. It will allow more operational flexibility by having a two-dimensional image detector.

Measured from one or more values for one or more wavelengths and angle of incidence α The spectrum can be measured in a manner described further below to measure the properties of the target structure T.

EUV reflection measuring device

Turning to FIG. 3, a metrology device 300 is provided for measuring the attributes of a metrology target T formed on a substrate W by the method of FIG. 2. Various hardware components are shown schematically. The practical implementation of these components can be performed by those skilled in the relevant arts based on well-known design principles using existing components and a mix of specially designed components. A support (not shown in detail) is provided for holding the substrate in a desired position and orientation relative to other components to be described. The radiation source 330 provides radiation to the lighting system 332. The illumination system 332 provides a radiation beam represented by a ray 304 (together with other rays forming the illumination beam) forming a focused irradiation spot on the target T. Conveniently, the detector 312 and any auxiliary optical components may be considered as the detection system 333.

The substrate W in this example is mounted on a movable support with a positioning system 334 so that the incident angle α of the rays 304 can be adjusted. In this example, the tilting substrate W is selected in accordance with convenience to change the angle of incidence, while the source 330 and the lighting system 332 remain stationary. In order to capture the reflected rays 308, the detection system 333 is provided with an additional movable support 336, so that the movable support moves relative to the stationary lighting system by an angle 2α, or relative to the substrate by an angle α. In a grazing incidence system for reflection measurement, it is convenient to define the angle of incidence α by referring to the plane of the substrate as shown. Of course, the incident angle can also be defined as the angle between the incident direction of the incident ray 304 and the direction N perpendicular to the substrate.

In alternative embodiments, the angle of incidence may be changed in more than one dimension, for example, by using a conical mounting table. This type of configuration and its potential benefits are described in detail in European Patent Application No. 15160786 mentioned above. The entire text of his application is incorporated herein by reference.

An additional actuator (not shown) is provided to bring each target T to a position where the focused radiation spot S is positioned. (On the other hand, bring the light spot to the position where the target is located.) In practical applications, there can be a series of individuals to be measured on a single substrate. The target or target part, and there may also be a series of individual targets or target parts to be measured on a series of substrates. In principle, it is not important whether the substrate and the target move and reorientate when the lighting system and the detector remain stationary, or whether the substrate remains stationary when the lighting system and the detector move, or by such techniques Whether the combination achieves different components with relative movement. The invention encompasses all such variations.

As already described with reference to FIG. 2, the radiation reflected by the target T and the substrate W is split into a spectrum of rays 310 of different wavelengths before it hits the detector 312. A second detector 338 for measuring the intensity of the incident light beam will also typically be provided for reference. The processor 340 receives signals from the detectors 312 and 338. The resulting reflection data for one or more angles of incidence is used in the processor to calculate a target's attributes (e.g., CD or overlay).

Inverse Compton Scattered Radiation Source

FIG. 4 is a schematic block diagram of a radiation source 330 in the apparatus of FIG. 3. In order to provide a high throughput rate and / or a high measurement density per wafer to a metrology device 300 that can be used as a primary metrology tool in the semiconductor industry, extremely bright sources are required. In order to detect the product structure in EUV, a wavelength range of about 13 nanometers is correlated, which is similar to the wavelength used for EUV imaging in the latest lithographic devices. However, within this wavelength range, dense high-luminance sources are not available on the market today. The inventors have identified that sources based on inverse Compton scattering (ICS) can be developed as sources suitable for use as source 330 in device 300. It is expected that ICS-based sources can provide the high brightness required for different kinds of scattering measurements and reflection measurements in the EUV range. The same or similar sources can also provide X-ray radiation for GI-SAXS or T-SAXS applications. Tunable sources with high brightness in the range of, for example, 0.01 nm to 125 nm are conceivable. This tunable source will be beneficial for scattering measurements (fixed angles, or in combination with angular scanning). If the source produces radiation with a certain level of spatial coherence, it can also be used in so-called lensless imaging techniques (coherent diffraction imaging (CDI), which includes, for example, what is called ankylography and stack Imaging (ptychography).

The radiation source 330 in this example is between the high-energy electron beam 400 and the laser radiation 401. Based on the interaction. A brief description of the main components and operations is provided here. For more details on the implementation of the ICS source, refer to "Compact x-ray source based on burst-mode inverse Compton scattering at 100kHz" by WS Graves et al. (Physical Review Special Topics-Accelerators and Beams 17, 120701 (2014) ). The entire reference of Graves et al. Is incorporated herein by reference.

Components associated with the electron beam are a radio frequency (RF) electron gun 402, a linear accelerator (linac) 404, a focusing assembly 406, a beam deflector 408, and an electron cutoff 410. The electron gun 402 contains a photocathode and an accelerator, so that an electron beam can be emitted into the linear accelerator 404 when triggered by an optical pulse 412 from a photocathode laser 414. The focusing assembly 406 may, for example, include a collection of quadrupole electromagnets. The deflector 408 may include a dipole electromagnet.

The seed laser 416 provides a pulse of seed radiation to the photocathode laser 414. In the example described by Graves et al., These pulses are pulses with a wavelength of 1030 nm, which has a pulse frequency of 200 MHz. The photocathode laser 414 in operation selects a group of pulses, optically amplifies them, and converts them to pulses with a wavelength of approximately 250 nm by generating a fourth harmonic. These pulses are pulses delivered to a photocathode to produce an electron beam. Pulses of, for example, a frequency of 100 kHz, 100 pulses per group, and 1000 groups per second can be selected. The linear accelerator 404 accelerates electrons to an energy in the range of, for example, 8 MeV to 40 MeV. Therefore, an electron beam 400 is generated and delivered to the interaction point IP using well-defined energy per electron. The beam is focused to its narrowest point at the point of interaction marked as IP. After passing through the interaction point, the deflector 408 redirects the electron beam to the electron cut-off 410.

The laser beam 401 is generated by an ICS laser 420. This laser beam is also seeded by a pulse picked up from the output of the seed laser 416. A pulse was obtained at 1 kHz, and the pulse was amplified and compressed to produce a pulse having a pulse length of 3 picoseconds at 1 kHz, which has a wavelength of 1030 nm. The output beam 422 of the ICS laser 420 is delivered into an optical cavity 424 formed between two mirror surfaces 426, 428. Figure 5 shows an enlarged detail of the optical cavity and interaction points. Section.

Referring to FIG. 4 and FIG. 5 together, the mirror surface 426 at the input end of the cavity is a two-way color mirror in order to transmit some wavelengths and reflect other wavelengths. The mirror surface 428 is a fully reflective mirror surface. The cavity 424 also contains a lens 430 and a harmonic generator 432. Harmonic generator 432 (e.g., lithium triborate (LBO) or barium borate (BBO) crystals) converts a proportion of incoming photons in beam 422 into 515 nm by frequency doubling (second harmonic generation) Of the wavelength. By the action of the dichroic mirror 426, these photons are trapped in the cavity to form a light beam 401 that interacts with the electron beam 400. The mirror surface 426 is also curved to provide a focusing function. The lens 430 and the mirror 426 focus the trapped laser beam 401 so as to define the beam waist at the desired interaction point IP. In a practical example, the directions of the laser beam 401 and the electron beam 400 are aligned as closely as possible while still avoiding interference between the electron beam and the laser optics. Graves et al. Used, for example, an angle of 50 mrad. The angle is exaggerated in the drawings, which are not to scale.

By these means, it has been arranged that while there are pulses of dense laser radiation, a string of 100 electron beams reaches the interaction point IP 100 times / second. The inelastic scattering between the electrons and photons in the two beams transfers extra energy to the photons, so that a proportion of the photons reach the desired frequency to produce the desired output beam with a photon of the desired wavelength for use in the metering method of FIG. 2 440. The output beam 440 has a relatively small divergence of, for example, 10 mrad, and a reflective focusing optic 442 is provided to focus the output beam to the desired radiation spot S. In that regard, the focusing optics 442 may be considered as a component forming the illumination system 332 of FIG. 3 and / or as a component forming the source 330. For use at EUV wavelengths, in this example, the optical member 442 may include a multilayer mirror, or a simple metal mirror such as Au or Ru metal. The focusing optics 442 can also be used as a beam splitter to provide reference illumination to the detector 338 (not shown in FIG. 4). Beam splitting can be performed, for example, by a grating structure integrated in the focusing optics. Beam splitting can be performed by a separate element (in the preferred case).

Returning to the generation of the electron beam 400, the electric power for the generation of the electron beam 400 is provided by the klystron 450 and the waveguide system 452 at a radio frequency. These klystrons 450 and waveguide systems 452 The voltage and current are controlled by the control system 454. The voltage on the linear accelerator determines the acceleration and final energy of the electrons in the beam 400. This directly affects the energy imparted to the laser photons, and therefore, the wavelength of the radiation forming the output beam 440 is determined. In the example of Graves et al., An x-ray source is required and generates a photon with an energy of 12.4 keV, which corresponds to a wavelength of about 0.1 nm in the x-ray band. This x-ray source may be useful in semiconductor metrology, but only useful in grazing incidence. This source can be used, for example, in T-SAXS, and can be more suitable for high-volume measurements than conventional plasma sources (which are not so bright) or synchrotron sources (which are too large and expensive). However, x-rays in grazing incidence are indeed not suitable for investigating surface structures in small localized areas on a wafer. With energy of 13 keV or greater, x-rays can be used to transmit through silicon wafers. The inventors have further recognized that ICS sources designed to produce hard x-rays can be adapted and adjusted to generate lower energy photons (longer wavelengths) simply by reducing the energy of the electrons. In this example, this is achieved by reducing the voltage supplied to the linear accelerator, which can be done very quickly by the appropriate design of the control system 454 and other components. Instead of or in addition to changing the linear accelerator voltage, or when the source does not use a linear accelerator, an equivalent step to adjust the energy of the electrons may be applied.

Therefore, the source 330 can be used to generate soft x-rays or EUV radiation at high brightness, instead of or as an alternative to "hard" x-rays. This would be an additional advantage if the source could also be adjusted to produce hard x-rays. For the main purposes envisaged herein, EUV can be generated, for example, in the energy (wavelength) range including 1 keV (approximately 1.2 nanometers), 0.1 keV (12.4 nanometers), and even 0.01 keV (124 nanometers) radiation. These wavelengths, which also correspond to the dimensions of the product features whose parameters are to be measured, allow large angles of incidence, and therefore allow finer focused light spots.

In addition, although the conventional plasma source is extremely variable in brightness throughout the EUV spectrum, the ICS source described here can be tuned to practically interest by proper control of the voltage and other parameters around the electron gun and linear accelerator. Any desired frequency in the frequency band. Not only Change the wavelength between different measurements, and also change the wavelength within a measurement, for example, to get "spectrum" information.

In addition, by further reducing the electron energy, in principle the same source can be used at longer wavelengths at so-called VUV (for example, 100 nm to 200 nm or 125 nm to 200 nm) and UV (200 nm Meters to 350 nanometers) and even visible light (400 to 800 nanometers) bands. Focusing optics 442 (although effective at EUV wavelengths) can also be servoed to focus radiation up to the visible wavelength range. If we only want UV or visible radiation sources, ICS sources will be overly complex and expensive. However, having a single source and optical system that is operable to produce this wide variety of wavelengths substantially only by electronic control changes allows new flexibility in the metrology device 300. This device can be useful not only in semiconductor manufacturing, but also in a wide range of applications for scientific investigations and / or quality control applications.

Optical system for EUV reflection measurement

Example applications of this source 330 include EUV reflection measurements using a device such as the device illustrated in FIG. 3. In this EUV-SR to metrology application in semiconductor manufacturing, small grating targets can be used. The detector 312 is used to capture multiple diffraction spectra, and simultaneously set the grazing incidence angle α to various values. In the case of using the detected spectrum and mathematical model of the target structure, reconstruction calculations can be performed to achieve the measurement of CD and / or other parameters of interest. An example reconstruction method will be explained further below.

In the case where the target illustrated in FIG. 2 is considered as an example, the size of the line and space will depend on the target design, but the period of the structure may be, for example, less than 100 nm, less than 50 nm, less than 20 nm , Even less than 10nm and down to 5nm. The lines of the grating structure may have the same size and pitch as the product features in the product area of the substrate. Merely for measurement purposes, the lines of the grating structure may in fact be the lines of the product structure, rather than the lines of the target structure formed in a dedicated target area. These small features can be formed, for example, in an EUV lithography process by embossing lithography or by a direct writing method. Modern DUV lithography can also be used to form these small features by a so-called double patterning process (usually multiple patterning). This class Other techniques include, for example, doubling the spacing between lithography-etching-lithography-etching (LELE) and self-aligned bimetal damascene in a back end-of the line (BEOL) layer. For the purpose of explanation, CD will be assumed in the following examples as the parameter of interest. However, where there are two gratings formed on top of each other, another parameter of interest may be a superimposed pair. This parameter can be measured based on the asymmetry in the EUV-SR diffraction order, as described separately below. The angle of incidence can be increased if necessary to achieve proper penetration into the substructure.

In a multi-patterning procedure, a structure is not formed in one layer of the product in one patterning operation but in two or more patterning steps. Therefore, for example, the first group of structures and the second group of structures can be staggered, and these groups can be formed in different steps in order to achieve a higher resolution than that produced by a single step. Although the placement of the population should be the same and perfect relative to other features on the substrate, of course, each actual pattern exhibits a certain positional offset. Any unintentional positional shift between groups can be considered as a form of superposition and can be measured by techniques similar to those used to measure superposition between layers. In addition, the overlapping pairs of features in the bottom layer or the overlying layer can be different for each group when multiple groups of features are formed in a single layer, and can be measured separately for each of these groups as needed. Overlap.

Figure 6 illustrates the change in elongation of the radiant light spot, which can be challenging to implement intra-granular metrology using grazing incidence reflection measurements. In (a) of FIG. 6, the substrate W and the target T are shown in a cross section. A representative incident ray 304 and a reflected ray 308 are described, and form an incident angle α with respect to the substrate W. Because these rays are representative rays, it should be taken into account that the incident radiation as a whole contains many rays, which rays form the light beams indicated schematically at 602. Similarly, the reflected radiation contains a number of rays 308 that form a beam of light as indicated schematically at 604. In order to take advantage of the smallest possible target, the rays of the light beam 602 are focused such that they converge to precisely define the minimum beam diameter where they meet the surface of the substrate W to form a radiant light spot. In this description, the incident light beam 602 is converged to a focal point, which has a minimum diameter d _B. The reflected light beam 604 (with neglect of scattering effects) contains scattered rays as shown. Because the grazing incidence angle α is relatively small (in other words, it is closer to zero than the closeness to 90 °), the diameter d _S of the radiation beam 602 projected on the target T is several times larger than the beam diameter d _B. The ratio between the diameters d _S and d _B depends on the sine of the angle α, as shown in (a) of FIG. 6.

As shown in FIG. 6 (b), in order to achieve a circular light spot S that fits in the area of the target T, the light beam 602 should have a strong elliptical cross section shown at B. When the angle α is, for example, 5 °, the minimum diameter d _{B of the} light beam should be more than 10 times smaller than the allowable diameter d _{S of the} light spot (sin5 ° = 0.087). For lower incidence angles, the minimum diameter of the beam will have to be tens, hundreds, or even thousands of times smaller. In practice, it will not be possible to obtain a light spot that fits in a small target area such as 5 square microns. Even at α = 5 °, the minimum beam diameter d _B should be about 436 nm to achieve a spot size below 5 microns. In contrast, as seen in (c) of FIG. 6, the increase in the grazing incidence angle α greatly relaxes the minimum diameter requirement of the light beam 602. The ellipse B 'can be much wider than the ellipse B in order to achieve a light spot S' in the region that fits the target T. For example, for α = 20 °, the beam diameter will only increase by three times. The minimum diameter d _B can be as large as 1.7 microns, which does not exceed a spot size of 5 microns.

Compared to known technologies, especially X-ray reflection measurement (GI-XRS), the use of EUV wavelengths in the range of 1 nm to 100 nm will allow these higher incidence angles and can bring in EUV optics Smaller spot size within design capabilities. This capability of the source 330 described above enables EUV reflection measurements to be considered for measuring small targets on substrates in high-volume manufacturing.

FIG. 7 illustrates a possible configuration of the lighting system 332 in the device of FIG. 3, and also illustrates a portion of the detection system 333. The radiation source 330 based on inverse Compton scattering generates radiation in a well-defined radiation beam 440 as described above with reference to FIGS. 4 and 5. Some or all of the components of the optical system shown can be omitted when not necessary to use this source to achieve the desired performance.

An EUV radiation beam 440 having a desired wavelength is received at a certain divergence. At source 330 At the radiation exit (to the entrance of the lighting system 332), a first aperture 620 is provided for use as an entrance pupil for the lighting system. An incident light beam 622 having a smaller divergence is irradiated on the focusing optical element or system. This focusing system is implemented in this description by a two-dimensionally curved mirror surface 624 (for example, an ellipsoidal mirror surface). The mirror surface 624 generates a convergent beam 626 that is focused to form a light spot at a target location on the substrate W. Optionally, a second aperture 630 is provided to define the diameter of the light beam 632 at the target. In detail, the aperture 630 can be adjusted in height and / or width so that different shapes of the light beam B ′ can be generated according to different needs / sizes and different incident angles α. It should be understood that the curved mirror 624 corresponds to the focusing optics 442 shown in FIG. 4.

The reflected beam 634 enters the detection system 333, and the reflected beam carries information about the structure of the target to the detector 312 (not shown in this figure). Optionally, a second focusing mirror 636 is provided to reduce the divergence of the light beam when it enters the detection system 333. Any of the two-dimensionally curved mirrors 624, 636 may be replaced with a series of two or more one-dimensionally curved (cylindrical) mirrors. As illustrated, the mirror 624 can also be used as a beam splitter to provide reference illumination to the detector 338. Beam splitting can be performed, for example, by a grating structure integrated in a mirror. Other changes in the optical system are of course possible without departing from the principles of the invention.

Wavelength selection

The ability to perform measurements at different wavelengths can greatly increase the auxiliary processor PU's use of methods such as optical scattering measurements to accurately measure the information diversity of nanostructures. It is possible to use an ICS source to select a wavelength and set it close to or at the absorption edge of a particular material to enable the possibility of, for example, material-dependent scattering measurement or imaging.

Figure 8 illustrates the interaction of different wavelengths of radiation with various materials that are just the choice of materials encountered in typical semiconductor products. In the four graphs, the horizontal axis represents the wavelength λ on a logarithmic scale, which just extends from 0.1 nm to 40 nm for the sake of example. As already mentioned, these wavelengths cover the size of the feature of interest and the measurement to be made Resolution. The vertical axis in each graph represents the penetration depth (attenuation length) in microns, or a given density of material. The absolute scale is not relevant, but it can be seen that each material exhibits a strong difference in the attenuation of the wavelength at either side of certain "edges", and that these edges decrease at different wavelengths for different elements and compounds.

For example, in the top graph, silicon Si exhibits a strong edge 700 at approximately 12.4 nanometers. Measurements at wavelength 702 are relatively sensitive to the presence of silicon, while measurements at wavelength 704 are relatively insensitive to the presence of silicon. In the second graph, the oxygen show a different edge 710, and in the third graph, the oxide SiO ₂ exhibits two edges corresponding to the components 720, 722, Si, and O components. The carbon in the fourth graph has an edge 730 at another wavelength. Therefore, it will be seen that the resist structure (which is high with respect to carbon) can be measured more accurately by selecting the wavelength 732 rather than some arbitrary wavelength. For further accuracy, at the cost of additional illumination and detection steps, a difference measurement can be obtained by detecting a scattering pattern or reflectance at wavelengths 732 and 734 on either side of edge 730. Similar difference pairs of wavelengths on either side of edges 700 and 710 are illustrated. The same measurement strategy is applied to, for example, Ge.

The application of an ICS source that utilizes the tunability of the wavelength of the emitted illumination is a metering application, in which wavelengths from the visible to the EUV range are used to provide information about the parameters of the lithography process, while using shorter than typical EUV generated by the ICS source The wavelength is used for measurements related to characterizing material properties. For example, while changing the wavelength of an ICS source, measure the roughness or topography of the underlying structure. For longer wavelengths, roughness information is hardly present in reflected illumination, while shorter wavelengths are more sensitive to local variations in configurations such as surface roughness. It is also found that there is a threshold for the wavelength of illumination where the configuration information no longer exists. Additional material-related information obtained for shorter wavelengths is material stoichiometry, density, electrical properties, and / or optical properties (such as conductivity and capacitance).

Compared to the available plasma-based EUV sources, the controllable change in wavelengths using ICS technology will not cause a wide change in source brightness. The compromises and damage associated with known sources can be largely avoided.

Application examples in high-volume manufacturing

FIG. 9 illustrates a substrate W that is one of a batch or batch of wafers undergoing processing in the facility of FIG. 1. A detector is used at each target site 900 to capture one or more scattering patterns. The scattering pattern is used by the processor 340 to calculate measurements and reported to the operator, LACU 206, and / or SCS 238. Although a semiconductor substrate (wafer) is cited as a specific type of product to be measured using an inspection device with an ICS source of the type described herein, it should be understood that the capability of a device with this source is applicable to a wide range of inspection And measurement tasks.

Although the target structure T in the form of a grating has been illustrated and described above, the method permitted by the present invention can be adapted to be not limited to use for periodic target structures, nor is it limited to structures dedicated to metrology. The target structure can be a component of a product structure. Product structures for this purpose include not only structures pre-sent in the finished product, but also structures that exist at intermediate stages in the manufacturing process, such as resist patterns or hard masks.

Although a product in the form of a processed semiconductor substrate has been described, another product to be inspected is a photomask or a reduction mask used as a patterning device in a lithographic apparatus. The target structure may be a part of this patterned device. Inspection can be performed during and after patterned device manufacturing for quality control. Detection may be performed periodically during use of the patterned device, for example to detect damage or contamination.

The structures under test in the examples have applied patterns and structures formed from these patterns. However, the method of the present invention can also be applied to the detection of a base substrate for a semiconductor product or a patterned device. The testing under that condition can be used for the measurement of layer thickness or composition, and / or for the measurement of uniformity, and / or for the detection of defects such as damage and contamination.

FIG. 10 illustrates the same apparatus for performing an enhanced measurement method, in which detectors are used at each target site or at different target sites to capture multiple scattering patterns (the wavelengths are switched each time). The results of these different wavelengths are combined into a single measurement by the processor 340 and reported to the operator, LACU 206, and / or SCS 238. The number of different wavelengths can be as small as two Or it may be ten or more. The high brightness of the ICS source, coupled with the ability to switch wavelengths in less than a second, less than half a second, or even less than a tenth of a second, allows these multiple measurements to be made at high output rates.

In the case of using an example of a spectral reflection measurement method, the purpose of the metrology technique is to calculate the measurement of one or more parameters of the shape. Where, for example, reconstruction techniques are used, strict optical theory is effectively used to calculate which values of these parameters will cause a particular observed reflection spectrum (as appropriate, including one or more high diffraction order spectra). In other words, target shape information is obtained for parameters such as critical dimension (CD) and overlapping pairs. The critical dimension (or CD) is the width of an object "written" on a substrate, and is the limit that a lithographic device can physically write on a substrate. In some cases, the parameter of interest may be CD uniformity rather than an absolute measurement of the CD itself. Other parameters such as grating height and sidewall angle can also be measured as needed. The stack measurement is a measurement system for measuring the stack of two targets to determine whether the two layers on the substrate are aligned.

Where the results from the EUV metrology device 300 are used in conjunction with the modeling of a target structure (such as target T) and its reflection and / or diffraction properties, the measurement of the shape and other parameters of the structure can be performed in several ways . In the first type of program, a first estimated diffraction pattern based on the target shape (first candidate structure) is calculated, and the diffraction pattern is compared with the observed reflection patterns at different wavelengths. Then the parameters of the model are systematically changed and the reflection spectrum is recalculated with a series of iterations to generate new candidate structures and thus achieve the best fit. In a second type of program, reflection spectra for many different candidate structures are calculated in advance to generate a "library" of reflection spectra. Then, compare the reflection spectrum observed from the measurement target with the calculated spectral library to find the best fit. Two methods can be used together: a rough fit can be obtained from the library, followed by iterative procedures to find the best fit. We expect that in the EUV spectral reflection measurement, the calculations used for the first type of procedure will be less onerous. In that case, library procedures will not be necessary.

These types of procedures are known in principle to those skilled in the art and can be adapted to A metering device 300 with an ICS radiation source is used.

FIG. 11 illustrates the same device performing different enhanced measurement methods, in which detectors are used at each target site or at different target sites to capture multiple scattering patterns (the wavelengths are switched each time). The results of these different wavelengths are used by the processor 340 to obtain different measurements of different parameters. For example, a conventional measurement target can be measured using visible wavelength radiation measurement, and then the product structure can be measured using EUV radiation. Again, the results are reported to the operator, LACU 206 and / or SCS 238.

Potentially, the dedicated optical scatterometer 240 of FIG. 1 may be replaced by functions included in the EUV metering device 244.

The application and benefits of these hybrid metering technologies are disclosed in my European patent application 14168067.8, filed on May 13, 2014, which was not published on this priority date. In that example, an optical scatterometer is used to measure one type of target, and an x-ray metrology device is used to measure other targets by T-SAXS. In the present invention, the same source can be used for both measurements.

FIG. 12 illustrates a combination of the principles of FIGS. 10 and 11, in which multiple types of measurements are performed on the same or different targets, and each type of measurement uses multiple wavelengths on the same target.

All these different modes of operation are greatly facilitated by providing a high-luminance source that can be quickly switched between different wavelengths across the EUV band and, optionally, across shorter and / or longer bands.

FIG. 13 illustrates the application of the source 330 in the T-SAXS metering device 1300. This metering device is similar to the device of FIG. 3 except that the substrate is presented at or near normal incidence with the radiation beam 1304, except that the detector 1312 is located behind the substrate. The other component symbols beginning with "13" are actually similar to the component symbols beginning with "3" in FIG. If the source produces x-rays, this source can be used for T-SAXS. For silicon products, a photon energy greater than 13keV will be most effective, and the energy currently used in T-SAXS is 17keV. However, even the energy obtained in the example of Graves et al., 12.4keV, can be sufficiently high (at a given source brightness). Case) to make T-SAXS feasible. Depending on the mechanical configuration, it is possible that the positioning system 1334 can move the substrate between the reflection measurement position shown in FIG. 3 and the transmission position shown in FIG. 13 within the same appliance. To simplify the mechanical design, the detectors 340 and 1340 can be separate detectors. A reference detector (not shown) can be provided again to measure the intensity of the illumination in real time.

FIG. 14 illustrates the application of a measurement method (for example, the method described above) in the management of a lithography manufacturing system. The steps are listed here and then explained in more detail:

S21: Process the wafer to produce a structure on the substrate

S22: Measuring CD and / or other parameters across the substrate

S23: Update the metering formula

S24: Update lithography and / or program recipe

At step S21, a lithography manufacturing system is used to generate a structure across the substrate. At S22, EUV metrology device 244 (eg, metrology device 300) is used and other metrology devices and information sources are used as appropriate to measure the properties of the structure across the substrate. At step S23, the measurement formula and calibration of the measurement device and / or other measurement device 240 are updated in view of the obtained measurement results.

At step S24, the measured values of the CD or other parameters are compared with the desired values, and the measured values are used to update the settings of the lithographic device and / or other devices in the lithographic manufacturing system. By providing an EUV metering device with a large capacity output rate, the performance of the entire system can be improved. Even at the smallest technology nodes, product features and / or product-like features can be directly measured, and targets within the grain can be provided and measured without consuming too much area.

In the above steps, it is assumed that enough targets are measured across one substrate and across multiple substrates so that a statistically reliable model of the program can be derived. It is not necessary to express the profile of CD and other parameters completely as changes across the substrate. For example, it can be expressed as a field profile common to all fields (each example of patterning using the patterned device MA at different locations on the substrate W) and repeatedly overlapping superimposed field-changing low-order fields Between changes. Adjusted in step S24 The settings of the lithography program may include on-site settings and on-site settings. These settings can be applied to all operations of the device or specific to a specific product layer.

in conclusion

Based on the described example metering device using ICS-based sources, those skilled in the art should understand that the same type of source can be used in a variety of applications and metering systems, not just for EUV spectral reflection measurement and EUV reflection Measured. For example:

-If the source produces x-rays, it can be used for T-SAXS, as already explained.

-GI-SAXS becomes more feasible: when trying to limit the spot size at these shallow incident angles, taking into account the loss of photons can be huge. The brightness and angular spread of the ICS source means that GI_SAXS can also become feasible in large-capacity environments.

-If the ICS source can be controlled to produce radiation with sufficient spatial coherence, additional metering techniques become available. Coherent diffraction imaging (CDI) methods have become of interest, such as stacked imaging. The choice of high source brightness and wavelength becomes useful because, for example, in stacked imaging, multiple images must be acquired in that technique to capture the phase of the scattered wave. Similarly, other CDI technologies require high-resolution data capture. For these CDI technologies, high brightness is also a key enabler.

-As mentioned, radiation in the VUV, DUV, UV, and visible light ranges can be generated by providing appropriate control and power supply configurations to the electron gun and linear accelerator.

Although specific embodiments of the invention have been described above, it should be understood that the invention may be practiced in other ways than described. Associated with novel objectives as implemented on substrates and patterned devices, an embodiment may include a computer program containing one or more sequences of machine-readable instructions describing the generation of objects on the substrate, A method of measuring targets on a substrate and / or processing measurements to obtain information about lithography procedures. This computer program can be executed, for example, in unit PU in the device of FIG. 3 and / or in control unit LACU of FIG. 2. A data storage medium (eg, semiconductor memory, magnetic disk, or optical disk) in which the computer program is stored can also be provided.

Although a patterned device in the form of a physical mask has been described, the term "patterned device" in this application also includes information that conveys a digitally-formed pattern, such as used in conjunction with a programmable patterned device product.

Further embodiments according to the invention are provided in the following numbered items:

1. A method of measuring an attribute of a structure, the method comprising: irradiating the structure with radiation at least for the first time; detecting the radiation after interacting with the structure; and determining the attribute based on an attribute of the radiation A property of the structure, wherein the radiation is generated by inverse Compton scattering, and the radiation has a first wavelength in a range of 0.1 nm to 125 nm.

2. The method of clause 1, wherein the structure is irradiated with the radiation using a beam diameter ranging from less than 10 microns and optionally less than 5 microns.

3. The method according to item 1 or 2, wherein the same structure is irradiated at least a second time and radiation is detected, the second time the radiation is generated by inverse Compton scattering and has a range of A second wavelength within this range of nanometers.

4. The method of clause 3, wherein the property of the structure is determined based on the detected radiation at both the first wavelength and the second wavelength.

5. The method of item 1, 2, 3 or 4, wherein the same structure or a different structure is irradiated at least a second time and radiation is detected, and the second time the radiation is caused by inverse Compton scattering Is generated and has a second wavelength outside the range of 0.1 nm to 125 nm.

6. The method of clause 5, wherein the second wavelength is shorter than 0.1 nm.

7. The method of clause 5, wherein the second wavelength is longer than 125 nm.

8. The method of clause 5, wherein the second wavelength is longer than 200 nm.

9. The method of clause 5, wherein the second wavelength is longer than 350 nm.

10. The method of any one of clauses 3 to 9, wherein the first time and the second time are completed in less than one second.

11. The method according to any of the preceding clauses, wherein the radiation is generated by simultaneously delivering an electron beam and a photon beam to an interaction point.

12. The method of clause 11, further comprising adjusting the wavelength of the radiation one or more times by adjusting an energy of an electron in the electron beam.

13. The method of clause 11 or 12, wherein an electron gun and a linear accelerator are used to generate the electron beam.

14. The method according to any one of the preceding clauses, wherein the structure is formed on a semiconductor substrate.

15. The method of clause 14, wherein an angle between a direction of the irradiation and a direction parallel to the substrate is greater than 2 °.

16. A radiation source device based on inverse Compton scattering, the device comprising: an electron source and a photon source; and a controller for controlling the electron source and the photon source to convert one or more electrons The beam spot and a pulse of photons are delivered to an interaction point at the same time, whereby a proportion of the photons obtain additional energy by inverse Compton scattering to the device and the device outputs the proportion of the photons, The additional energy can be controlled such that the photons output by the device have a wavelength in a range of 0.1 nm to 125 nm.

17. The device of clause 16, wherein the additional energy is controllable such that the photons output by the device have a wavelength that is freely selectable across at least a sub-range of the range from 0.1 nm to 100 nm.

18. The device of clause 16 or 17, wherein the additional energy can be further controlled such that the photons output by the device at another time have a wavelength outside the range of 0.1 nm to 100 nm.

19. A measuring device for measuring the properties of a structure, the device comprising: a radiation source device as in any one of clauses 16 to 18; an illumination system for converting photons output by the radiation source device Delivered to the structure in a radiation beam; and a detection system for detecting radiation from the structure after the photons have interacted with the structure.

20. The device of clause 19, wherein the radiation beam has a range of less than 10 microns and optionally less than 5 microns when projected onto the structure.

21. The device of clause 19 or 20, further comprising a controller for changing the wavelength of the radiation in the radiation beam, and simultaneously detecting the radiation multiple times.

22. The device of clause 21, wherein the controller is operable to set a new wavelength and detect radiation at least twice in one second.

23. The device of any of clauses 19 to 22, wherein the detection system is configured to detect the radiation after reflection from the structure.

24. The device of clause 23, wherein the illumination system and the detection system are adapted to measure properties of structures formed at various locations on a semiconductor substrate, and wherein a surface of the substrate is relative to a surface of the substrate, One of the radiation beams has an incident angle greater than 2 °.

25. A device manufacturing method, comprising: using a lithography program to transfer a pattern from a patterned device to a substrate, the pattern defining at least one structure; measuring one or more attributes of the structure to determine the Applying a value to one or more parameters of the lithography process; and applying a correction in the subsequent operations of the lithography process according to the measured attribute, wherein the step of measuring the attributes of the structure includes using a Measure an attribute as in any of clauses 1 to 15.

26. The device manufacturing method according to item 33, wherein the functional device pattern defines a product feature with a critical dimension of less than 50 nm and optionally less than 20 nm.

Although specific reference may be made above to the use of embodiments of the present invention in the context of optical lithography, it will be understood that the present invention can be used in other applications (e.g., embossed lithography) and where the context allows The following is not limited to optical lithography. In embossed lithography, the configuration in a patterned device defines a pattern that is generated on a substrate. The configuration of the patterned device can be pressed into a resist layer supplied to a substrate on which the resist is applied by applying electricity Cured by magnetic radiation, heat, pressure, or a combination thereof. After the resist is cured, the patterned device is removed from the resist, leaving a pattern in it.

The terms "radiation" and "beam" used with respect to lithographic devices cover all types of electromagnetic radiation, including the areas identified above.

The term "lens" may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic, and electrostatic optical components, as the context allows.

The foregoing description of specific embodiments will thus fully reveal the general nature of the invention: without departing from the general concepts of the invention, others can easily adapt to various applications by applying the knowledge of those skilled in the art Modify and / or adapt these specific embodiments without undue experimentation. Therefore, based on the teaching and guidance presented herein, such adaptations and modifications are intended to be within the meaning and scope of equivalents of the disclosed embodiments. It should be understood that the wording or terminology herein is for the purpose of, for example, description rather than limitation, so that the terminology or wording of this specification should be interpreted by those skilled in the art in light of the teachings and the guidance.

The breadth and scope of the present invention should not be limited by any of the above-mentioned exemplary embodiments, but should be defined only based on the scope of the following patent applications and their equivalents.

Claims (14)

A method of measuring a property of a structure, the method comprising: irradiating the structure with radiation at least for the first time; detecting the radiation after interacting with the structure and after reflecting from the structure; and based on An attribute of the radiation determines an attribute of the structure, wherein the radiation is generated by inverse Compton scattering, and the radiation has a first wavelength in a range of 0.1 nm to 125 nm. The method of claim 1, wherein the radiation is irradiated with the beam using a beam diameter ranging from less than 10 microns and optionally less than 5 microns. The method of claim 1 or 2, wherein the same structure is irradiated at least a second time and the radiation is detected, the second time the radiation is generated by inverse Compton scattering and has a range of 0.1 nm to 125 nm A second wavelength within this range. The method of claim 1 or 2, wherein the same structure or a different structure is irradiated at least a second time and the radiation is detected, the second time the radiation is generated by inverse Compton scattering and has a range of 0.1 nm. A second wavelength outside the range to 125 nm. The method of claim 3, wherein the first time and the second time are completed in less than one second. The method of claim 1 or 2, wherein the radiation is generated by simultaneously delivering an electron beam and a photon beam to an interaction point. The method of claim 6, further comprising adjusting the wavelength of the radiation one or more times by adjusting an energy of an electron in the electron beam. The method of claim 6, wherein an electron gun and a linear accelerator are used to generate the electron beam. A measuring device for measuring the properties of a structure, the device includes: a radiation source device based on inverse Compton scattering, the device includes: an electron source and a photon source; and a controller, the controller is used for Controlling the electron source and the photon source to simultaneously deliver one or more electron beams of electrons with a pulse of a photon to an interaction point, whereby a proportion of the photons pass through to the device Inverse Compton scattering acquires additional energy and the proportion of photons output by the device, wherein the additional energy can be controlled so that the photons output by the device have one of the range of 0.1 nm to 125 nm Wavelength; an illumination system for delivering photons output from the radiation source device to the structure in a radiation beam; and a detection system for removing the photons from the structure after the photons have interacted with the structure Structural detection of radiation. The device of claim 9, wherein the radiation beam has a range of less than 10 microns and optionally less than 5 microns when projected onto the structure. The device of claim 9 or 10, further comprising a controller for changing the wavelength of the radiation in the radiation beam, and simultaneously detecting the radiation multiple times. The device of claim 11, wherein the controller is operable to set a new wavelength and detect radiation at least twice in one second. The device of claim 9 or 10, wherein the detection system is configured to detect the radiation after reflection from the structure. The device of claim 13, wherein the illumination system and the detection system are adapted to measure properties of structures formed at various locations on a semiconductor substrate, and wherein the radiation is relative to a surface of the substrate One of the light beams has an incident angle greater than 2 °.